EDG treats reference return from await_resume() as an rvalue instead of an lvalue.

[zaides-blackduck]

Issue Summary

when await_resume() returns a reference to a value EDG treats it as an rvalue instead of an lvalue. This generates an error when the returned value is assigned.
The error in the example:

    (co_await bool_ref_awaiter{}) = false;
    ^

Reproducing Source Code

namespace std {
  template <typename = void> struct coroutine_handle;
  template <> struct coroutine_handle<> { void *address(); };
  template <typename> struct coroutine_handle {
    static coroutine_handle from_address(void *);
    operator coroutine_handle<>() noexcept;
  };
  template <typename R, typename...> struct coroutine_traits {
    using promise_type = typename R::promise_type;
  };
} // namespace std

struct suspend {
  bool await_ready() noexcept;
  void await_suspend(std::coroutine_handle<>) noexcept;
  void await_resume() noexcept;
};

struct bool_ref_awaiter {
  bool await_ready() noexcept;
  void await_suspend(std::coroutine_handle<>) noexcept;
  bool &await_resume() noexcept;
};

struct task;

struct promise {
  suspend initial_suspend() noexcept;
  suspend final_suspend() noexcept;
  void return_void();
  void unhandled_exception();
  task get_return_object();
};

struct task {
  using promise_type = promise;
};

task f() {
  (co_await bool_ref_awaiter{}) = false;
}

Command-line Options

cafe --c++23 test.cpp

Type of Issue

[Front End] This code SHOULD compile with these options.

Additional Details

Runs well with Clang 20 and gcc 15

Reproducing (Standard) Configuration(s)

No response

Reproducing (Non-standard) Configuration

No response

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• The reproducing source code that I have provided does not depend on headers that I have not included with my submission.
• I have reduced the reproducing source code to the best of my ability.
• I have selected at least one standard configuration or uploaded a non-standard configuration dump.
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